buckle

deflate, flatten, melt, melt down

break, break down, conk (out), crash, die, fail, give out, stall

burst, shatter, smash, splinter, split

crack, crumble, pop, snap

readdress, reapply

knuckle down, set (to), settle (down)

busy, commit, concern, engage, involve

exert, exhaust, put out, spend, strain, stress, tax, trouble, wear out

carry on, pitch in, plunge (in)

grind, hump, hustle, peg (away), plod, plow, plug (away), work